1. Field of the Invention
The present invention relates to transformer clips used to retain transformers on printed circuit boards, and, more particularly, to an improved transformer clip for use in high density electronic systems, wherein said clip uses a spring action to retain a magnetic core assembly together while encompassing minimum space above the board.
2. Description of the Prior Art
Transformers are required in electronic circuits for various reasons, such as transforming a high voltage to a lower voltage level, to provide isolation, inter alia. For minimum power loss, it is necessary to mount the transformers in proximity to their associated circuit hardware. Methods have been devised to mount the transformers on printed circuit boards (PCBs), which are utilized in electronics because the wiring between components can be done effectively with minimum line length, resulting in less line loss, and with maximum isolation, resulting in less spurious and/or coupled noise.
The accustomed practice of mounting transformers onto PCBs is generally accomplished by inserting the legs of the transformer, or of its casing, through pre-drilled holes in the PCB and soldering the legs to the bottom of the board. This allows for simple installation and removal. The transformer terminals, which are cut to a specified length, are also inserted into pre-drilled holes to contact the appropriate conductive path for the circuit.
Further development of the PCB-mounted transformer has yielded a transformer component in which portions of a magnetic core are wound with conductive material and are thereafter held together with a clip. Alternatively, a spool can be wound with wire and encased between core portions. The clip is formed in a spring-like configuration to exert a compressive force on the magnetic core portions while providing legs for mounting the transformer to the PCB. Prior configurations of the spring-like transformer clips included clips utilizing a spring located on the top of the clip to compress the core components together, as well as those employing a spring situated on the bottom of the clip for compression.
As the electronics technology has advanced, the need for smaller, more compact electronics assemblies has increased. To accommodate the need for more compact assemblies, a higher density of PCBs per assembly is desired. The spacing limitation between two PCBs, although limited by thermodynamic and electrical limitations inherent in electronic assemblies, is naturally constrained to the height of the tallest component on the board below. Because most of the components used on PCBs are integrated circuits (ICs), resistors, and capacitors, which are all fairly low lying, transformers tend to be one of the taller components used. It is critical that their height be kept to a minimum to maximize the number of PCBs that may be employed in a card rack of predetermined width.
As can be seen in FIGS. 1 and 2, transformer halves 10 of a prior art transformer assembly 20 are held in juxtaposition utilizing the transformer clip 12. The assembly 20 is held to the PCB 14 by legs 16 of the clip 12 which are inserted into holes in the PCB 14 and are attached thereto using solder 15. A spring-like configuration 17 of the clip 12 compresses the two transformer halves 10 together. Because the clip spring 17 is configured on the top, as in FIG. 1, or on the bottom of the clip, as in FIG. 2, the transformer clip height is not minimized, thereby not allowing maximization of PCB density.